Metallic shield for electrical conductors



\ MIG/e Oct. 3, 1944. J. J. MAscucH 2,359,436

METALLIC SHIELD FOR ELECTRICAL CONDUCTORS Filed April 27, 1929 v .AS

/ r 1 TTORNEY.

Patented st. 3, 1944 METALLIC sms'np FOB OONDUCTORS osFics ELECTRICAL Joseph J. Mascuch, Newark, N. J.,- assigns: to Breeze Corporations, Inc., Newark, N. J

Application April 21, 1929, Serial No. 358,711 (01'. 123-169) 2 Claims.

This invention relates to metallic'shielding for electrical conductors and has for an object to protect insulated conductors by a metallic covering which is grounded-thereby preventing radiationfrom the. conductors and corresponding disturb' ces in radio active apparatus. A particular se of this invention is the shieldingoi' the conductors leading to the spark plugs of the engines in airplanes so that the use of radio sis-'- naling on the airplanes may be possible.

The spark plug conductors leading from the distributor are subject to high tension currents and require heavy insulation and should have a certain degree of flexibility. In the'present invention a porcelain elbow is mounted on the top entering it at one end and engasins'the post of the plug. In order that the elbow and the conductcr may be metallically shielded on their entire outer surfaces,- the elbow is coated with metallic foil, applied, if necessary, by an adhesive,

, and the conductor is similarly coated; these coatings connect with the metallic body of the spark plug and are thereby grounded to the engine.

The metallic foil may be applied in various waysto the outside of the insulation, however, I prefer to electro-plate the elbow and theconductor; also to electroplate the cable-in which the conductor may be embedded,'afterthe cable has'been formed to shape; By a process herein described, I am able to electro-plate non -metallic substances andto form alight metallic coating on articles of various shapes, such as the con ductors used on internal combustion engines;

. This invention will bemore particularly underducing surface on the porcelain. In this state stood from the following specification and from the accompanying drawing selected to illustrate one form of my invention, in which, Fig. 1'is a sectional elevation on an enlarged scale of a spark plug with a shielded conductor according of the spark plug having'the insulated conductor 1 the conductor 2| and stem ll through the clip 20,

Fig. 2 which clamps the stem as the conductor 2| is inserted in the elbow. A metallic cap 22 is screwed on the end of the elbow as indicated at 23 and may be sealed to the elbow l5 through the channel 24 by the application'of a suitable sealing medium, or the edge of 23 may be spun into channel 24 to prevent cap 22 from unscrew- The elbow is preferably made from unglazed porcelain and provided with ridges at 28. It may be coated with shellac or other waterproof adhesive to which the metallic foil is applied, making a grounded connection with the cap I3.- The rubber insulation of the conductor 2| may be similarly treated so that the metallic coating is grounded through 22 and the coating of the elbow tothe cap l3.

The preferred way of pplying the metallic r011 go to elbow and to the rubber covering of the conductor is by electro-platin'g. This makes a uniform coating over the entire surface of a light metal such as nickel which is rust proof and has a high tensile strength, and addsvery little to 25 the weight of the conductors; at the same time sufiicient flexibility is maintained in the conductors for the purposes intended. v In order to electro-plate a non-metallic substance it is necessary to metalize its surface so that it will conduct the electric current. The

to this invention; 'Fig. 2 is a detail showing one method of connecting the conductor to the spark plug within tlie elbow; Fig. 3 is a form.ofcable that may be used between the distributor and .spark plugs of an engine and Fig. 4 is a crosssection of the cable in Fig. 3.

In the'drawing, is'the engine head, I2 is the porcelain elbow is metallized by spraying the unglazed surface with shellac and then spraying with bronze powder, preferably in a volatile solution. This power quickly dries and leaves a conelectro-plating vat 0 the metalizedsurface becomes a uniform con.-

ductor, after this stage is reached, it has been found that one volt is sufiicient for a copper plating solution for these articles; After a foundation of copper plating is applied the device is then transferred to a nickel plating vat for a thin despark plug body which is screwed into the engine head, I3 is the cap, I4 is the stem and i5 is the porcelain elbow to protect the outlet of the stem. The elbow is seated in the cap on the asbestos gasket i'i and is secured in place by the spun-- over edge of the cap at l6. A nut l9 on the end of stem It holds the insulation in Place.

.-posit of nickel. j

The plated surface is indicated at 21. F g. and forms a continuous metallic shell'over the irregular form of the elbow. Ifan unequal shrinkage should develop between this shell and spark plugs of amultiple cylinder engine are, in Connection is-made in the chamber i8 between the present case, formed into a cable as indicated in Fig. 3 which is moulded to the shape desired with the individual conductors fanning from the end of this cable.

This cable is electro-plated after it is formed, by metalizing the surface of the rubber insulation as described in connection with the porcelain and applying a copper and nickel deposit thereto.

The cable 3| is indicated as an elbow a of moulded rubber 36 in which the conductors 32, 33, 34 and 35 are embedded. Each of these conductors comprise a rubber insulated, stranded wire which terminates in the eyelets shown. The

rubber insulation is sometimes braided and may bebraided with wire in an ordinary braiding machine. This surface is coated with metallic powder and plated with copper and nickel as described. The plating is indicated at 31 which covers the entire surface including the outlet of the cable at 38 and the exposed surface of each of the conductors as indicated on conductor 2| at 31. Y

It has been the practice to place the conductors in flexible metallic hose but this has not proven' quite satisfactory for airplane work and does not form a continuous closed metallic covering for the conductor.

Having thus described my invention, I claim:

1. In combination, a spark plug comprising a metallic cap and'a stem having an outlet, a conductor connecting to said stem at the outlet, a dielectric member seated against said cap and enclosing said outlet, a metal cap screwed on the end of said member and having an aperture for said conductor, and a metallic coating intimately encasing said member and said conductor, said coating and said .caps being electrically connected.

2. In a spark plug of the type having a cylinder engaging shell carrying one electrode and a shielded conductor electrically connected to the other electrode, the combination with said conductor and shell of a shield having a cylindrical portion secured at its lower end bydirect, locking contact with said shell and a second angularly-directed portion embracing the end of said conductor and electrically connected with the shield thereof and means for holding the two portions of 'said shield in engagement with each other whereby an electrical connection is maintained from the shield of said conductor through the two portions of said shield to said shell.

JOSEPH J. MASCUCH. 

